Boring bit

ABSTRACT

A boring bit comprising a hollow body having a cavity therein for the storage of a lubricant, a pair of discharge passages in communication with the cavity for directing the lubricant and a pair of cutting blades mounted in the bit. The body passages are each provided with an aligned straight-walled portion adapted to mount one of the cutting blades. At least two guide rollers are mounted in the body with their axes of rotation lying in planes substantially parallel with the rotational axis of the bit and substantially perpendicular to the planes of the cutting edges of the blades.

United States Patent [191 Hlocky June 11, 1974 BORING BIT [75] Inventor: Ladislav Hlocky, Banovce nad Bebravou, Czechoslovakia [73] Assignee: TATRA, narodni podnik,

Loprivnice, Czechoslovakia [22] Filed: Oct. 6, 1972 [21] Appl. No.: 295,688

[52] US. Cl 408/59, 408/226, 408/238, 408/713 [51] Int. Cl B23b 51/06 [58] Field of Search 408/57, 59, 228, 713, 226, 408/238 [56] References Cited UNITED STATES PATENTS 3,010,345 11/1961 Wagner 408/59 FOREIGN PATENTS OR APPLICATIONS 1,200,127 7/1970 Great Britain 408/57 Primary Examiner-Andrew R. .1 uhasz Assistant Examiner--Z. R. Linsky Attorney, Agent, or FirmMurray Schaffer [5 7] ABSTRACT A boring bit comprising a hollow body having a cavity therein for the storage of a lubricant, a pair of discharge passages in communication with the cavity for directing the lubricant and a pair of cutting blades mounted in the bit. The body passages are each provided with an aligned straight-walled portion adapted to mount one of the cutting blades. At least two guide rollers are mounted in the body with their axes of rotation lying in planes substantially parallel with the rotational axis of the bit and substantially perpendicular to the planes of the cutting edges of the blades.

5 Claims, 3 Drawing Figures PATENTEBJuu I I m V saw 108- a PATENTEDJuu 1 I \914 SHEET 30F 3' 1 BORING BIT BACKGROUND OF THE INVENTION The present invention relates to a boring bit and in particular to a bit for boring holes in solid material.

Boring bits are generally provided with one or more cutting blades located in a body. The bit includes a reservoir for a cooling lubricant and discharge passages for said oil. As is well known, undue stresses are placed upon the guide rollers because of the manner and position in which such guide rollers are mounted in the boring bit with respect to the cutting blades. This has resulted in uneven and premature wear of such guide rollers. Further, the cutting blade which forms the apex of the cutting cone of the bit is also subjected to excessive stress during the boring operation, since, due to its mounting arrangement in the forward section of the bit,

the desired supportive forces for the blades are not properly developed.

It is the prime object of the present invention to provide an improved boring bit for forming precise holes in solid material such as metals, which overcomes the disadvantages of the prior art devices.

It is, therefore, an object of this invention to provide a boring bit adapted to mount the guide rollers therein in such manner that there is a more uniform distribution of stresses thereon and a resultant increased service life therefore.

It is another object of this invention to provide a boring bit in which the cutting blades are so mounted therein with respect to the guide rollers and oil discharge passages that the desired supportive forces for said blades are developed during the boring procedure thereby increasing the service life of such blades.

It is a further object of this invention to provide a boring bit in which the cutting blades and guide rollers are so juxtaposed that the degree of rotational vibration during the boring ,operation is maintained at a minimum.

Other objects and advantages of the invention will become readily apparent from a consideration of the ensuing description of the invention.

SUMMARY OF THE INVENTION According to the present invention there is provided a boring bit having a pair of cutting bladesand guide rollers for positioning the bit within a borehole. The bit comprises a hollow body portion provided with a cavity for the storage of a cooling fluid. The body terminates in a cutting head in which a pair of fluid discharge passages is formed in communication with the cavity. The body passages are each provided with straight-walled portions for detachably mounting the cutting blades. At least two guide rollers are mounted in the body portion with their axes in a plane substantially parallel with the axis of the rotation of the bit and substantially perpendicular to the planes of the cutting edges of said blades.

Preferably, the cutting blades are detachably mounted so as to be easily replaced, and are arranged so that their frontal cutting planes lie within a common diametrical plane.

Further, according to the present invention, the straight-walled portions are provided with notches cut as recesses in which the blades are mounted, so that only their cutting edges are exposed. The rollers are diametrically arranged in the bit between the cutting blades and have their circumferential surfaces extending beyond the circumference of the bit to contact the bore hole formed and to guide the bit.

Because of the particular juxtapo sitioning of the cutting blades and guide rollers there has been such a distribution of operating forces that the service life of both the cutting blades and guide rollers have been substantially increased.

In order that the invention may be more fully comprehended, it will now be fully described, by way of example, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a plan view of the bit with the cutting blades and guide rollers mounted therein;

FIG. 2 is a side elevational view of the bit shown in FIG. 1, partly in cross-section, taken along the lines 2-2 of FIG. 1; and

FIG. 3 is a side elevational view of the bit shown in FIG. 1, partly in cross-section, taken along the lines 3-3 of FIG. 1.

DESCRIPTION OF THE INVENTION Turning to the drawings, the boring bit of the present invention comprises an elongated substantially cylindrical body 1 having a longitudinal axis of rotation about the center line 0. The head of the body I is formed with a conical surface 2 which is interrupted by a pair of open passages 3 and 4 shaped in a horizontal cross-section in a triangular or heart-like configuration. The body 5 has an axial bore forming a hollow interior cavity 5 which serves as a reservoir for the storage of cooling or lubricating fluid used to facilitate the cutting operation. The lubricating fluid is conventional and customarily comprises an oil of relatively low viscosity. The cavity 5 communicates the passages 3 and 4 which serve for discharge of the lubricating oil to the cutting blades during operation of the bit. The bore of the body 1 is provided with a threaded interior wall 9 below the cavity 5 to which a guide rod and/or drill shaft (not shown) may be attached.

As will be seen from FIGS. 1 and 3, the discharge passage 3 is formed with one of its radial walls 6 extending straight outwardly from the axial center of the body 1. This straight-wall 6 is provided with a V-shaped recess 7 formed like a notch having its apex extending downwardly axially of the body. The open mouth of notch 7 extends radially from approximately the axial center line of the body 1 into a point about a fourth of the way to the circumferential edge of the body, as defined by the circle 0' seen in FIG. 1. A flat muIti-sided cutting blade 10 is located in the notch 7 and is secured firmly by a fastening screw or similar clamping means. The cutting blade 10 shaped with edges conforming to the shape of the V-shaped notch so it fits firmly and will not loosen during use. The blade 10 is formed with angled cutting edges 12 and 12' which are substantially the only portions of the blade rising above the conical surface 2.

By referring to FIGS. 1 and 2, it will be seen that the passage 4 is similarly formed with a radially extending straight-wall section 8, which is also provided with a V- shaped recess at its upper edge forming a notch 9. The open mouth of the notch 9 extends from the circumference of the body 1 radially inward, well short of the axial center as seen in FIG. 2. A second cutting blade 11 is mounted within the notch 9 by a suitable screw fastener or similar means. The blade 11 is five-sided, the sides of which angle to conform to the sides of the V-shaped notch 9 so as to seat firmly therein. The blade 11 is also provided with two cutting edges 13 and 13' which are substantially the only portions of the blade extending above the conical surface 2 and outwardly of the circumference of the body 1, respectively, as seen in FIG. 2.

As seen more clearly in FIG. 1, the straight-walled portions 6 and 8 and their notches 7 and 9, respectively, are dimensioned so that the appropriately formed flat cutting blades are diametrically aligned and form cutting planes R-R which pass through the center of the body 1. A superior and balanced cutting is obtained in this manner, although a suitable boring bit can be obtained if the blades were not ideally aligned in this manner, but somewhat offset.

It will be also noted that the blades 10 and 11 are easily replaceable and may even be rotatable to present different cutting faces or edges. Since the receiving notches 7'and 9 for the blades are fixed and uniformly spaced in the bit, the new blades require little balancing when inserted.

The boring bit is further provided with a pair of rotatable guide rollers 14 and 15 which are positioned at substantially diametrically opposed locations relative to each other between the cutting blades. The rollers 14 and 15 having circumferential wall extending beyond the circumference of the body and are mounted on pivot axles 14a and 15a which are arranged parallel to the central longitudinal axis of the body 1 and substantially in a parallel axial plane at right angles to the frontal cutting planes of the respective blades 10 and 11.

The boring bit of the present invention is eminently suitable for use in drills or boring tools used to form precise holes in solid material such as metal. The position of the blades, the location of the lubricating passages and the position of the guide rollers permits the boring of long-and accurate holes with a virtual absence of skew, unwanted vibrational forces and the creation of undesirable heat. It will be obvious that both the cutting blades are firmly supported and provided with a substantial wall section by which the stresses of the operation are fully absorbed. Furthermore, the stresses are more uniformly distributed about the boring bit.

Changes and modifications will be obvious to those skilled in this art. Accordingly, it is intended that the present disclosure be taken as illustrative of the present invention and not as limiting of its scope.

What is claimed:

1. A boring bit having a pair of cutting blades comprising a hollow body portion provided with a cavity for the storage of a lubricant, said body terminating in a cutting head and having a pair of discharge passages in communication with said cavity for directing said lubricant therefrom, said body passages being each provided with a straight-walled portion to mount a cutting blade, the edges of said blades being aligned coplanar substantially parallel to the axis of the rotation of the 1 bit, a guide roller being mounted in each of said body passages, said rollers being disposed substantially opposite each other and having their axes of rotation in a plane substantially parallel with the axis of rotation of said bit and substantially perpendicular to the planes of the cutting edges of said blades.

2. A boring bit according to claim 1 wherein the head of the bit terminates in a conical surface and said discharge passages extend through the body of the bit and terminate in openings in said conical surface in diametrically opposed relation to each other and between said straight-walled portions.

3. A boring bit according to claim 2 wherein a notch is provided in each of said straight-walled portions adapted to mechanically mount one of said cutting blades therein.

4. A boring bit according to claim 3 including detachable fastening means for removably mounting said blades.

5. A boring bit according to claim 1 wherein two of said guide rollers are provided, said guide rollers being positioned at substantially diametrically opposed points of the bit circumference. 

1. A boring bit having a pair of cutting blades comprising a hollow body portion provided with a cavity for the storage of a lubricant, said body terminating in a cutting head and having a pair of discharge passages in communication with said cavity for directing said lubricant therefrom, said body passages being each provided with a straight-walled portion to mount a cutting blade, the edges of said blades being aligned coplanar substantially parallel to the axis of the rotation of the bit, a guide roller being mounted in each of said body passages, said rollers being disposed substantially opposite each other and having their axes of rotation in a plane substantially parallel with the axis of rotation of said bit and substantially perpendicular to the planes of the cutting edges of said blades.
 2. A boring bit according to claim 1 wherein the head of the bit terminates in a conical surface and said discharge passages extend through the body of the bit and terminate in openings in said conical surface in diametrically opposed relation to each other and between said straight-walled portions.
 3. A boring bit according to claim 2 wherein a notch is provided in each of said straight-walled portions adapted to mechanically mount one of said cutting blades therein.
 4. A boring bit according to claim 3 including detachable fastening means for removably mounting said blades.
 5. A boring bit according to claim 1 wherein two of said guide rollers are provided, said guide rollers being positioned at substantially diametrically opposed points of the bit circumference. 